1. Field of the Invention
The present invention relates to an industrial X-ray generator designed to drive electrons emitted from a cathode to hit an anode and thereby generate X-rays from the anode so as to be used for non-destructive examinations of structures such as pipes of plant piping.
2. Description of the Related Art
X-ray generators having a cathode formed by using a tungsten filament as electron source are known. For example, Jpn. Pat. Appln. Laid-Open Publication No. 6-267692 (Patent Document 1) discloses such an X-ray generator. Generally, the filament is electrically energized and heated to not lower than 2,000° C. in order to make it emit thermal electrons. A high voltage is applied to the filament. Therefore, when an X-ray tube and an X-ray power source are arranged in a single unit for an industrial X-ray tube, the X-ray tube and the X-ray power source are sealed in high-pressure gas containers in order to establish insulation. For example, Jpn. Pat. Appln. Laid-Open Publication No. 3-149740 (Patent Document 2) discloses such a technique.
Conventional industrial X-ray generators using high-pressure gas containers are accompanied by a problem of bulkiness and heavyweight because high-pressure containers have to be used. An X-ray generator and a control unit typically weigh about 30 kg when put together.
Industrial X-ray generators having a cathode formed by using a filament require an arrangement for cooling the power source for filament and also the filament section to give rise to a problem of being large and heavy.
Industrial X-ray generators designed to use a molded member for electrically insulating the high-voltage section thereof instead of using gas for insulation are also known. For example, Jpn. Pat. Appln. Laid-Open Publication No. 6-267692 (Patent Document 3), Jpn. Pat. Appln. Laid-Open Publication No. 2001-135496 (Patent Document 4) and Jpn. Pat. Appln. Laid-Open Publication No. 2001-135497 (Patent Document 5) disclose such X-ray generators.
However, Jpn. Pat. Appln. Laid-Open Publication No. 6-267692 (Patent Document 3) only discloses an apparatus where only a cable receptacle and an X-ray tube are covered by a molded member and hence it does not provide a compact and lightweight insulated structure where both a high-voltage section and an X-ray tube are covered by a molded member.
Jpn. Pat. Appln. Laid-Open Publication No. 2001-135496 (Patent Document 4) and Jpn. Pat. Appln. Laid-Open Publication No. 2001-135497 (Patent Document 5) disclose apparatus where an X-ray tube and a high-voltage generating section are arranged at mutually unrelated respective positions and the high-voltage generating section is electrically insulated by a molded member.
Since an X-ray tube and a high-voltage generating section are arranged at mutually unrelated respective positions in each of these known apparatus, the entire apparatus including an X-ray tube and a high-voltage generating section inevitably becomes large.
Additionally, while a high-voltage generating section is so designed that a low voltage of about several kV is applied to its input terminal and it outputs a high voltage of tens of several kV to a hundred and tens of several kV from its output terminal, no appropriate consideration is given to the positional arrangement of the high-voltage site and the low-voltage site in either of the apparatus disclosed in Jpn. Pat. Appln. Laid-Open Publication No. 2001-135496 (Patent Document 4) and Jpn. Pat. Appln. Laid-Open Publication No. 2001-135497 (Patent Document 5). In other words, a sufficient distance needs to be provided between the high-voltage site and the low-voltage site and the molded member for shielding the high-voltage section requires a sufficient size and a sufficient volume to make any attempt at downsizing a difficult one.
Generally, in X-ray generators having an X-ray tube, industrial X-ray generators in particular, the X-ray tube and the high-voltage generating section need to be covered by an X-ray shielding member that is typically made of lead in order to prevent X-rays from leaking to the outside. As the X-ray generator becomes large, the X-ray shielding member also becomes large. Then, there arises a problem that the entire apparatus becomes very heavy due to the lead it contains.